Well completion method and apparatus for explosive stimulation

ABSTRACT

Disclosed is a method and apparatus for preventing damage to the tubular goods and cement sheath of wells during an explosive stimulation treatment. The invention includes the use of honeycomb structured casing joints to absorb the damaging shock energy emanating from explosions, used to stimulate producing zones, by the placement of the honeycomb casing in the casing string above and below the wellbore zone to be stimulated.

United States Patent ll i Land Sept. 12, 1972 [54] WELL COMPLETION METHOD AND 2,867,172 l/ 1959 l-Iradel ..166/299 UX APPARATUS FOR EXPLOSIVE 2,911,046 ll/1959 Yahn ..166/285 STIMULATION 3,110,346 11/ 1963 Spurlock et a] ..166/285 3,336,982 8/1967 Woodward et al. .......l66/299 [72] Invent Land Tulsa Okla 3,533,471 10 1970 Robinson ..166/299 Assigneer C1668 Service Oil o pany, Tul- 3,534,816 10/1970 Showalter ..166/298 X sa, kla. [22] Filed: Sept. 30, 1970 Primary Examiner-Stephen J. Novosad Attorney-J. Richard Geaman [21] Appl. No.: 76,893

[57] ABSTRACT [52] U.S. Cl. ..166/299, 166/63, 166/242 Disclosed is a method and apparatus f preventing [51] Int. Cl ..E21b 33/13, E2lb 43/26 damage to the tubular goods and cement sheath f [58] Field of Search ..166/285, 297-299, wells during an explosive stimulation treatment The 166/179 242; 102,22 invention includes the use of honeycomb structured casing joints to absorb the damaging shock energy emanating from explosions, used to stimulate produc- [5 6] References C'ted ing zones, by the placement of the honeycomb casing UNITED STATES PATENTS in the casing string above and below the wellbore zone to be stimulated. 3,064,731 11/1962 Hall ....166/297 2,986,217 5/1961 Johnston ..166/285 X 5 Claims, 3 Drawing Figures WELL COMPLETION METHOD APPARATUS FOR EXPLOSIVE STIMULATION BACKGROUND OF THE INVENTION This invention relates to the recovery of hydrocarbons and minerals from subterranean reservoirs. More particularly, it relates to the recovery of hydrocarbons by the use-of a method and apparatus for preventing damage to the tubular goods and cement sheath of production wells during an explosive stimulation treatment. t

In the primary and secondary production of natural gas, petroleum and minerals from subterranean reservoirs, often areas of low permeability are encountered. By permeability is meant the measure of the reservoirs capacity for transporting fluid throughits pores. This capacity'may be expressed in petroleum engineering units as darcies .or millidarcies, a darcy being that capacity of a reservoir rock required to allow flow of one cubic centimeter of one centipoise viscosity fluid through one centimeter square of rock per second under a pressure gradient of one atmosphere. Therefore, a given increase in permeability will result in the capability of an increase in fluid flow through that portion of the reservoir rock treated. An increase in the permeability within a reservoir is called stimulation, which is a required treatment for low productivity reservoirs.

When a reservoir rock is fractured, there exists an increase in the rock permeability with the flow of the reservoir fluids allowed into new portions of the reservoir matrix which were previously impermeable to fluid flow. During reservoir stimulation, an increase in permeability is established and greater flow of reservoir fluid is afforded through the stimulated areas. The production interval of the hydrocarbon or mineral containing reservoir is generally composed of strata of varying penneability. The low permeability areas are formed of a tight, low permeability material through which fluid How is restricted by the configuration of the rock matrix. Since few rock formations are homogeneous, the heterogeniety of the formation must be considered as a restraint on petroleum and natural gas production. It is desirable to treat the low permeability zones' of a reservoir by stimulation, thereby affording a greater capacity through which reservoir fluids may flow so as to subject a greater volume of reservoir to hydrocarbon or mineral recovery.

The conventional methods available for the combating of the heterogeneity of reservoirs involve complex stimulation techniques, such as hydraulic fracturing, acidizing or explosively detonating the less permeable reservoir zones. One of the earliest stimulation techniques was by the use of liquid explosives, for example nitroglycerin, in a wellbore opposite the uncased portion of the producing formation to be stimulated. A severe problem exists with the explosive stimulation of mineral, oil and gas wells in that associated with the stimulation is the destruction of the casing and cement sheath and loss of the necessary isolating cement bonds and the destruction of the casing and formation interfaces in the wellbore. The distortion of tubular goods and the destruction of the cement bonds contained in wells stimulated by explosive fracturing prevent subsequent efficient production. Also, shock waves, generated by the explosive stimulation treatment,

propagate up the casing and cement sheath and destroy the cement seal. The propagation of the explosive shock waves causes undesirable pressure and fluid in the casing between the producing zones within the production wellbore.

Conventional practices in explosive stimulation treatments generally involve stemming the well above the treatment interval by using cement, sand, gravel, and viscous fluids or a combination of these materials to pack a well and isolate the explosive detonation and shock wave propagation. The stemming practice confines the explosion, but does not provide protection to the well completion. What is required is a method and apparatus for preventing damage to the tubular goods and cement sheath of wells during explosive stimula tion treatments.

It is an object of this invention to provide apparatus for an improved reservoir and mineral deposit treatment technique.

It is another object of this invention to provide a method for the protection of the tubular goods and cement sheath in a well during explosive stimulation treatments.

It is still a further object of the present invention to provide apparatus by which the tubular goods contained within a wellbore may be protected during stimulation by explosive fracturing.

With these and other objects in mind, the invention is hereinafter set forth with particular reference to the following drawing and description:

SUMMARY OF THE INVENTION The objects of the present invention are accomplished by apparatus and a method for the explosive stimulation of a wellbore. The apparatus comprises a first conventional casing joint set to a distance above the wellbore section to be explosively stimulated. A first honeycomb casing joint is connected to the bottom of the first casing joint so as to be completed to the top of the wellbore section to be explosively stimulated. A second conventional casing joint is attached to the bottom of the first honeycomb casing joint so as to traverse the wellbore section to be explosively stimulated, with a second honeycomb casing joint connected to the bottom of the second conventional casing joint to complete the apparatus. Multiple completions of the apparatus of the present invention may be positioned for each zone in the wellbore to be explosively stimulated. The honeycomb casing joints in the completions may have one or more vertical flow ports at the top and bottom thereof through which cement may be circulated.

The apparatus for the explosive stimulation of a bottomhole section of a wellbore would comprise a first conventional casing joint set to a distance above the bottomhole section of the wellbore to be explosively stimulated. A honeycomb casing joint is connected to the bottom of the first conventional casing joint so as to be completed to the top of the bottomhole section. A second conventional casing joint is connected to the bottom of the honeycomb casing joint, the other end of which is spudded into the bottom of the hole.

The present invention also comprises a process for the explosive stimulation of a wellbore. The process comprises the completing and cementing of lengths of honeycomb casing above and below the wellbore section to be explosively stimulated, with a conventional casing joint positioned between the honeycomb casings so as to traverse the wellbore section to be explosively stimulated. The conventional casing joint is then perforated and explosive introduced through the perforations into the wellbore section. Subsequently, the explosive is detonated to stimulate the wellbore section.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention may be more fully understood by referral to the following drawings in which FIG. 1 represents a three-dimensional view of a preferred embodiment of the honeycombed casing apparatus of the present invention as positioned in order to provide explosive stimulation resistance for a casing completion;

FIG. 2 represents across-sectional view of the honey-combed casing as taken along the line 2 2 of FIG. 1 depicting the relationship of the honeycombed casing as it is utilized to isolate a wellbore and the casing cement sheath contained therein in order to provide adequate protection during explosive stimulation; and

FIG. 3 represents a top-sectional view taken along line 3 3 of FIG. 2 depicting a preferred arrangement of the honeycombed casing of the present invention.

DETAILED DESCRIPTION OF THE INVENTION The present invention discloses apparatus and a process for preventing damage to the tubular goods and cement sheath of a well during explosive stimulation of the well. The invention utilizes honeycomb structured casing sections to absorb the damaging shock energy emanating from explosions used to stimulate producing zones in a hydrocarbon or mineral bearing wellbore. In particular, the invention utilizes the placement of honeycomb casing joints in the vicinity of zones to be explosively treated in order to protect the wellbore completions and allow adequate explosive stimulation of the producing zones.

The present invention may be more fully understood by referral to one embodiment of the invention, as depicted in the drawing, for isolating damaging forces resulting from explosive stimulation of an intermediate zone in a wellbore. Honeycomb casing joints 101 and 102, having honeycomb networks 1 14 and 115, respectively, and tubing contained therein, are positioned in the casing string above and below a wellbore zone 112 to be treated with explosives. A first conventional casing joint 109 extends through a portion of the overburden rock 106 and is connected to honeycomb casing 101 by casing connector 108. Honeycomb joint 101 is then connected to a second conventional casing joint 103 by casing connector 104. Second conventional casing joint 103 traverses the wellbore zone 112, which will be explosively stimulated, and is connected to the second honeycomb casing joint 102 by easing connector .105. Honeycomb casing 102 is connected by easing connector 110 to third conventional casing joint 111. The apparatus of the present invention may be repeated in a like manner for as many productive zones in the wellbore which are to be stimulated by explosives.

The casing string arrangementdescribed, may be ccmentedinto place by either of two methods. In the first method, the conventional casing joints above the upper honeycomb casing joint 101 may be perforated and the cement squeezed through the perforations into the upper annulus. In a similar fashion, the cement may be circulated into the lower annulus. A second completion technique would involve honeycomb casing joints which contain vertical fluid passageways therethrough, as shown in FIG. 1 by ports 107 and 113, to allow cement to be circulated up the annulus without perforating. Once in place, the honeycomb casing joints would serve as a barrier against the damaging forces generated by the explosives.

To more particularly understand the disposition of the honeycomb casing of the present invention and the particular construction thereof reference should be had to FIG. 2. FIG. 2 is a cross-sectional view taken along line 2 2 of FIG. 1. In FIG. 2 the honeycomb casing joints 101 and 102, respectfully, having honeycomb networks 114 and 115 are positioned in the casing string above and below a wellbore zone 112 to be treated with explosive. Fluid ports 107 and 113 are provided in the honeycomb casing to allow the passage of cement through the casing joints while the major portion of the honeycomb casing remains empty and devoid of cement to absorb the subsequent explosive shock. A first conventional casing joint 109 extends through a portion of the overburden rock 106 and is connected to the honeycomb casing 101 by easing connector 108. Honeycomb joint 101 is then connected to a second conventional casing joint 102 by casing connector 104. A second conventional casing joint 103 is utilized to traverse the wellbore zone 112 and is completed to the wellbore wall by a cement sheath 216 which is continuous throughout the wellbore in proximity of production zone and has perforations 217 contained therein connecting the wellbore production tubing through casing joint 103. The second conventional casing joint 103 is connected to a second honeycomb casing joint 102 by casing connector 105. Honeycomb casing 102 is also connected by easing connector 110 to a third conventional casing joint 111 utilized for further repetition of the production tubing throughout the remainder of the wellbore.

To more particularly define the honeycomb arrangement of the present invention, a preferred embodiment of the disposition of the honeycomb network within the honeycomb casing is depicted in FIG. 3 wherein honeycomb casing joint 102 is depicted having honeycomb networks radially connecting the easing portion of the honeycomb casing 102 and fluid ports 113 forming a means for passing cement so as to provide a means wherein casing cement may be introduced within the honeycomb casing joint to allow an adequate case completion between the wellbore and the casing cement and provide a continuous cement sheath throughout the wellbore; but therein allowing shock absorbing means of the honeycomb network to provide reassurance of the casing sheath preventing breakdown of the casing cement sheath and allowing degradation thereof.

The arrangement of honeycomb casing joints may be placed at more than one depth interval in the well should there exist multiple zones in the well to be explosively stimulated. A bottomhole zone may also be 1 isolated by placing one or more honeycomb casing joints in the string immediately above the bottomhole zone. A conventional casing joint being connected thereto at the bottom of the honeycomb casing joint, fed through the wellbore zone of interest and spudded into the bottomhole of the well.

In the utilization of the apparatus of the present invention, the process for explosive stimulation of the wellbore involves the completing and cementing of the honeycomb casings above and below the wellbore sections to be explosively stimulated. Generally, from about to about feet of honeycomb casing above and below each zone to be stimulated is required to provide the necessary shock absorbing media. A conventional casing joint is positioned between the honeycomb casings so as to traverse the wellbore section to be explosively stimulated. Subsequent to the completion and cementing of the honeycomb casing joints and conventional casing joints at the various wellbore zones, the casing joints are perforated at the wellbore zones to be stimulated. After perforating is completed, explosive is introduced into the wellbore sections to be explosively detonated, through the perforated casing joints. Either sequentially or simultaneously, the explosive loaded wellbore sections are detonated to stimulate the wellbore sections of interest.

By positioning the honeycomb casing joints above and below the wellbore sections of interest, the shock waves generated by the explosive stimulation treatments do not propagate up the casing and cement sheath, thereby destroying the cement shield, but are absorbed in the honeycomb casing. This phenomenon is similar to the energy dissipation of exhaust gases from an internal combustion engine by their absorption and dissipation in the baffles of a muffler. The explosions shock waves are dissipated into the formation rather than up the casing string, thereby preventing damage to the tubing goods and cement sheath of the well during explosive stimulation.

Honeycomb casing and conventional casing joints utilized in the present invention may be constructed of any wellbore tubular good material, for example steel, aluminum, or plastic. The honeycomb casing must exhibit the requisite strength to withstand the shock waves generated by the explosive stimulation, exhibit corrosion resistance to contain the hydrocarbon fluids or mineral solutions produced from the formation, as well as yield a long service life for the production of the stimulated wellbores. In general, the honeycomb network will consist of multiple compartments of metal or other construction material within the annulus formed by two sections or joints of casing. The network may also be formed by injection of a foam material between the pipe sections as by the introduction of a urethane foam, etc.

By the use of the apparatus and process of the present invention, wellbore zones may be explosively stimulated and developed while protection is provided to the tubular goods and cement sheath contained therein. The process of the present invention presents a process by which the damage normally suffered by wellbore strings during explosive stimulation may be avoided while substantially increasing the effective drainage radius of the well. Therefore, by the use of the present invention it is possible to obtain stimulation in the vicinity of the wellbore desired while still retaining rigidity in those sections of the wellbore used for support of the lproduction and casing stringg.

While t e present invention has een described herein with respect to particular embodiments thereof, it will be appreciated by those skilled in the art, however, that various changes and modifications can be made without departing from the scope of the invention.

Therefore, I claim:

1. Apparatus for the explosive stimulation of a wellbore, comprising:

a. a first conventional casing joint completed to a distance above the wellbore section to be explosively stimulated:

b. a first honeycomb casing joint having ribbing therein through which cement may pass, connected to the bottom of the first conventional casing joint so as to be completed to the top of the wellbore section to be explosively stimulated;

c. a second conventional casing joint, connected to the bottom of the first honeycomb casing joint so as to be completed through the wellbore section to be explosively stimulated; and

d. a second honeycomb casing joint having ribbing therein through which cement may pass, connected to the bottom of the second conventional casing joint so as to be completed below the wellbore section to be explosively stimulated.

2. The apparatus of claim 1 in which at least one of the honeycomb casing joints has one or more vertical fluid passageways therein.

3. The apparatus of claim 1 further comprising multiple completions of the apparatus of steps (a) through (d) for each zone in the wellbore to be explosively stimulated.

4. Apparatus for the explosive stimulation of the bottom-hole section of a wellbore, comprising:

a. a first conventional casing joint completed to a distance above the bottomhole of the wellbore to be explosively stimulated;

b. a honeycomb casing joint having a ribbing therein through which cement may pass, connected to the bottom of the first conventional casing joint so as to be completed to the top of the bottomhole section; and

c. a second conventional casing joint connected to the bottom of the honeycomb casing joint, the lower end of such second conventional casing joint being spudded into the bottom of the well, so as to be completed through the wellbore section to be explosively stimulated.

5. A process for the explosive stimulation of a wellbore, comprising:

a. completing one or more honeycomb casing joints above and below the wellbore section to be explosively stimulated with a completed conventional casing joint positioned between the honeycomb casing joints so as to traverse the wellbore section to be explosively stimulated;

b. perforating the completed conventional casing joint;

c. introducing explosive into the wellbore section through the perforated casing joint; and

d. detonating the explosive. 

1. Apparatus for the explosive stimulation of a wellbore, comprising: a. a first conventional casing joint completed to a distance above the wellbore section to be explosively stimulated: b. a first honeycomb casing joint having ribbing therein through which cement may pass, connected to the bottom of the first conventional casing joint so as to be completed to the top of the wellbore section to be explosively stimulated; c. a second conventional casing joint, connected to the bottom of the first honeycomb casing joint so as to be completed through the wellbore section to be explosively stimulated; and d. a second honeycomb casing joint having ribbing therein through which cement may pass, connected to the bottom of the second conventional casing joint so as to be completed below the wellbore section to be explosively stimulated.
 2. The apparatus of claim 1 in which at least one of the honeycomb casing joints has one or more vertical fluid passageways therein.
 3. The apparatus of claim 1 further comprising multiple completions of the apparatus of steps (a) through (d) for each zone in the wellbore to be explosively stimulated.
 4. Apparatus for the explosive stimulation of the bottom-hole section of a wellbore, comprising: a. a first conventional casing joint completed to a distance above the bottomhole of the wellbore to be explosively stimulated; b. a honeycomb casing joint having a ribbing therein through which cement may pass, connected to the bottom of the first conventional casing joint so as to be completed to the top of the bottomhole section; and c. a second conventional casing joint connected to the bottom of the honeycomb casing joint, the lower end of such second conventional casing joint being spudded into the bottom of the well, so as to be completed through the wellbore section to be explosively stimulated.
 5. A process for the explosive stimulation of a wellbore, comprising: a. completing one or more honeycomb casing joints above and below the wellbore section to be explosively Stimulated with a completed conventional casing joint positioned between the honeycomb casing joints so as to traverse the wellbore section to be explosively stimulated; b. perforating the completed conventional casing joint; c. introducing explosive into the wellbore section through the perforated casing joint; and d. detonating the explosive. 